Agricultural implements known as combines are typically used for harvesting grain and cereal crops. Such machines are used for harvesting wheat, beans, corn, and other such crops.
In addition to severing the crop plant from the ground, combines thrash the severed plants to separate the grains from the stocks, husks, cobs, and other residue materials. After the thrashing process is performed upon the plants, the products of this process are conveyed to a sifting conveyer by which the grain is separated from the residue. Generally, after this separation has occurred the residue is distributed back on the ground worked by a spreader structure mounted at the rear of the combine.
The grain, however, after having been sifted, is conveyed to a storage bin. In many combines, this bin is located at a height above the structure by which thrashing and separating is accomplished. In order to raise the grain to the storage bin, an elevator is used.
When working of a particular field is completed, the combine returns to a storage silo or similar structure, and the grain carried in the storage bin is transferred to the silo.
Grain from plants recently severed from the ground typically contains a high moisture content. With almost all grains, some drying of the grain must be accomplished prior to placing it in the storage silo. If this drying were not effectuated, the grain could rot and become unholsum.
The prior art has taught the drying of the grain by a dryer positioned near the silo. After the grain is dried, an elevator transfers it into the silo. Another way in which drying is accomplished is by transferring the grain from the storage bin of the combine to an upward position in the silo by means of an elevator. With this type of drying, a dryer is mounted within the silo at this upward location. After the grain is dried, it is passed to a hopper from which it is discharged into the lower levels of the silo.
Drying of grains prior to storage by any of the methods discussed is extremely inefficient. Little drying is accomplished from the time the plant is severed from the ground until it is passed through a dryer unit positioned near the storage silo. Consequently, a significant amount of the farmer's time is wasted in drying the grain prior to storage. This is time that could be spent harvesting additional amounts of the grain.
In an effort to more efficiently utilize time, some prior art devices have attempted to effect the drying function, to a degree, while the combine is in the fields. U.S. Pat. No. 4,038,758 (Miller) discloses such a structure. The device of this patent uses radiators for circulating water from the engine block in order to preheat air that is forced through a heating element. With devices such as this, however, sufficient quantities of thermal energy are not available to accomplish a meaningful measure of drying while the combine is in the field.
Besides being inefficient with respect to time, methods of drying, as presently practiced, are also inefficient with respect to energy. This is true particularly with respect to corn. Shelled corn, in order to be safely stored, should not have a moisture content any higher than 15 percent. When severed from the ground, however, corn kernels have a moisture content between 20 and 24 percent. Under the most favorable circumstances, therefore, the kernels need be dried to eliminate 5 percent moisture. Under the worst circumstances, however, they need be dried to eliminate 9 percent.
At present energy prices, costs for drying one bushel of shelled corn to a point where it can be stored are at least 5 cents per percentage point of moisture content which must be eliminated. These costs appear to be applicable regardless of whether an electrical, natural gas, or fuel oil dryer is utilized.
The costs, therefore, for drying one bushel of shelled corn would range between 25 and 45 cents. When considering that six to seven billion bushels of shelled corn are harvested annually, one can see that an extremely significant energy expenditure is involved.
With crops such as beans and wheat, the energy expenditure is not quite as significant. Even still, however, not insignificant costs are involved with these crops.
It is to this situation that the invention of the present application is directed. The present invention is designed to economize on both the farmer's time and the costs involved in drying his grains for storage.